Cutting the final cord: How wireless power and wireless charging works

Christopher Null |
March 4, 2015

In the 1890s, Nikola Tesla captured the imagination of the world with his invention of the Tesla coil, a device that could transmit electricity through the air, no wires required. More than 100 years later, the world has responded by adapting this breakthrough technology... mainly to recharge their electric toothbrushes.

The A4WP promotes a resonant-coupling technology dubbed Rezence, which has yet to see any widespread commercial deployments, but there are a handful of PMA-certified products now on the market. And Starbucks, for its part, had previously announced plans to roll out PMA-compatible wireless charging pads in its stores nationwide after successful pilot projects in Boston and San Francisco.

Ultimately, all three of these technologies are all similar, but the materials used all differ in the values of their resonant frequencies and the power they generate. This isn't likely to be a major hindrance in the long term, though. Qualcomm senior director of wireless power solutions Mark Hunsicker says that device manufacturers can simply incorporate components that support both major technologies. "To implement a dual-mode receiver is relatively straightforward," he says.

Headlong into tomorrow

How might wireless power technologies be commercialized in the future? The deployment of mammoth Tesla coils to power entire neighborhoods is an unlikely possibility, but there might be a future for wireless power outside of keeping our phone batteries topped up. With resonant induction technology increasing the range of wireless charging, furniture manufacturers are integrating charging pads into desks, bar tops, and nightstands.

Someday, full surfaces may be energized with charging technology — not just tables but floors and walls as well. Safety is a concern with all of this, of course, because one of the by-products of wireless power is heat. "In the future, the entire industry wants to see an experience similar to Wi-Fi," says Hunsicker, "but there's a huge regulatory challenge there."

IEEE Fellow Stuart Lipoff notes that at this point "it's really not clear what people find useful or are willing to invest in," but he imagines a public wireless charging infrastructure that would free us from the tyranny of the two-prong plug. "Traffic lights at intersections would be an interesting wireless power spot" for both pedestrians and drivers, he says. It could even be easily monetized. "A wireless power station could simply look up your ID on your phone and charge you for the amount of electricity you transfer to it. With today's battery tech, you could charge your battery halfway in just a few minutes while waiting for a light to change."

Electric cars are another area where this technology is already on the rise. At CES this year, two companies, including BMW, demonstrated wireless vehicle-charging technology. Just park your car over a pad in your garage and the vehicle charges automatically.

What about putting chargers in the roadway then? While it's just a concept, it's an idea that could revolutionize road travel as we know it, keeping batteries topped up while we roll down the street.